Writing instrument



FIG. 1 is an elevational view of pen body in an exploded condition, with the cap member removed for convenience of illustration, all side being identical thereof;

FIG. 2 is a perspective view of the cap member with the pen body removed for convenience of illustration; and,

FIG. 3 is a perspective view of the pen body with the cap member removed for convenience of illustration. 

The ornamental design for a writing instrument, as shown and described. 